Relationships between chemical composition and decay durability of Coula edulis Baill as an alternative wood species in Gabon

Abstract

The general objective of this work was to evaluate the quality of the little-known tropical woods of the Congo Basin, particularly Coula edulis, while looking for new biocidal products. The natural durability of the hazel tree of Gabon Coula edulis versus basidiomycete fungi was evaluated with native and extracted samples of heartwood against brown rot (Rhodonia placenta and Coniophora puteana) and white rot (Trametes versicolor and Pycnoporus sanguineus) fungi. The results showed that non-extracted samples were more durable. Fungal growth inhibition tests using different concentrations of extractives confirmed the fungicidal effects. Percentage of the different wood polymers and GC–MS analysis of wood extractives were carried out to examine correlations between durability and wood chemistry. Natural durability of Coula edulis could be explained by the unusually high lignin content and the presence of high amounts of polyphenols like gallic and ellagic acids and tannins. Coula edulis could therefore be a local alternative to help alleviate wood shortages in Gabon.